The best thing to do is buy a tractor that you can get parts for. John Deere, New Holland/Ford and Kubota are all really popular around here, but you do pay for the name but it is much nicer to just drive to town, pick up the parts and go home then have to order online and hope you get the right parts. We bought a John Deere 3020 (about 70 hp) with a loader, hay forks and bucket and a metal shade on top for $10,000 about 4 years ago. Last winter we bought a John Deere 2040, no loader for $4,000. Having a loader is really nice, you can pick up things or get to higher places, stack things higher and if you make a deck to attach to your bucket you can even stand on it, have someone lift you up and trim trees, paint the house, etc. This isn't the safest thing to do but in some cases you can get higher with the loader than you can with a ladder. Plus if you get stuck you can actually use the loader to push or pull yourself out. We have a box blade and it works really well to clean the barns out, but we need to get a bigger one because the one we have is narrower than the tractor so you can't get right along the walls.
When looking at a tractor definitely look for leaks (especially around the cylinders on the loader! the seals on these can be very expensive to replace) even if the tractor is off you can usually tell if it has been leaking oil if it is all shiny/wet looking in any spots. You also want to make sure it shifts smoothly and that the steering is pretty good. Have the person lift the loader all the way up and all the way down to make sure the hydraulics work smoothly and don't make a lot of noise. If you ever go to look at one and it is already running or the engine is hot, leave that is a very good sign that the tractor is hard to start. Both of our tractors are diesels and they start just fine in any weather. We do plug in the bigger tractor to warm the glow plugs but it still just pops right off. Also make sure it already has at least one rear remote (hydraulic hookup) so if you need to hook up any piece of equipment and it has a hydraulic hose you already have it there. These are also pretty pricey to have put on.
Definitely look at the tires. Rear tractor tires are VERY expensive. The ones for our bigger tractor (they are 16.9 x 38) are about $1000 each. Front tires aren't as much but can be pretty high. Don't buy an off brand tractor, like a Yanmar. We had a Yanmar and it was nothing but trouble. It was an older one and was one that was originally made to be used in Japan, but it had a ton of problems and you can only order the parts. I wouldn't buy one from an auction, mostly because there is a ton of risk there. You don't know if the tractor is just there because the guy needs money or if it is there because it has some very expensive repair that needs done. For example, our big tractor needs the injection pump rebuilt which if we bought an already rebuilt one would cost about $1000. We can have ours rebuilt for $320 but that is still a pretty good chunk of change, and if we don't fix it the engine will get ruined because there is fuel getting in the oil making it thinner.
I don't really know what a good price to spend would be. I would expect to pay at least a few thousand for one, especially if you want one in good condition with a loader and everything else. Tractors are kind of like cars and any kind of upgrade, add on, etc costs and typically isn't very cheap, but you can do just about anything with a tractor if you have all the right attachments. Neither of our tractors are 4 wheel drive, but when it gets muddy it would be nice to have it. We do have weights for the rear tires on our bigger tractor which do help it get more traction.
If you go to
www.tractordata.com you can look up just about any tractor and get the specs on it like how many were made, years it was made, hp, tire size, engine size and other specs, etc. Very helpful and on some tractors it will even show the original price the tractor sold for.
thinking I could save a big chunk of change. I have a river of questions running through my head now. I was looking locally at these Mahindra's and Branson's 
